Children's suffix effects for verbal working memory reflect phonological coding and perceptual grouping.

When listeners recall order of presentation for sequences of unrelated words, recall is most accurate for first and final items. When a speech suffix is appended to the list, however, the advantage for final items is diminished. The usual interpretation is that listeners recover phonological structure from speech signals and use that structure to store items in a working memory buffer; the process of recovering phonological structure for a suffix interrupts that processing for the final list item. Although not mutually exclusive, another hypothesis suggests that perceptual grouping of list items and suffix based on common acoustic structure is necessary for the effect to occur. To evaluate these accounts as well as potential age-related differences, adults and 8-year-old children were asked to recall order of presentation for a closed set of nouns in five suffix conditions: none, auditory go, lipread go, a tone, and a colored circle. Overt articulation was prohibited, but attention to the suffix was mandated. Children's serial recall was generally poorer than that of adults, but patterns across list positions were similar for both age groups. Participants showed stronger effects for speech suffixes than for nonspeech suffixes regardless of whether suffixes were seen or heard, but effects were not restricted to final list items. And although effects of heard and lipread suffixes were similar for early list items, heard speech exerted greater effects on late list items. Outcomes suggest that some effect of heard and lipread speech suffixes arises from their shared phonological structure, but this effect is strongest when perceptual grouping occurs.